At present, during test procedure of a Liquid Crystal Module (LCM), a signal switching device is generally used for connection between a test apparatus and the LCM (i.e., a tested apparatus) since a port of the LCM is different from a port of the test apparatus.
FIG. 1 schematically shows a structure of a traditional signal switching device. As shown in FIG. 1, a test apparatus 30 is provided with high-speed signal test ports, low-speed signal test ports, and power source test ports. Each test port is electrically connected with a corresponding tested port of a tested apparatus 10 through a signal switching device 20. In general, each test port is electrically connected with a corresponding tested port through an electrical connector that is arranged on the signal switching device 20.
The electrical connection mode between the test apparatus 30 and the tested apparatus 10 through the signal switching device 20 in the prior art will be illustrated in detail hereinafter with reference to Table 1, Table 2, FIG. 2, and FIG. 3.
TABLE 1Test apparatusTested apparatus1D0P2D0N3CLKP4CLKN5D1P6D1N7LEDK8VCC9IOVCC10RESET11LEDA
TABLE 2Test apparatusTested apparatus1VCC2LEDK3D1P4D1N5CLKP6CLKN7D0N8D0P9RESET10LEDA11IOVCC
As shown by the definition of the ports in Table 1 and Table 2, the tested apparatus 10 is provided with 11 tested ports, among which there are 6 high-speed signal tested ports, i.e., D0P, D0N, D1P, D1N, CLKP, and CLKN. D0P and D0N form a pair of differential signal tested ports, D1P and D1N form a pair of differential signal tested ports, and CLKP and CLKN form a pair of differential signal tested ports. There are 3 low-speed signal tested ports, which are LEDA, LEDK, and RESET respectively. There are 2 power source tested ports, which are VCC and IOVCC respectively. As shown in Table 1, D0P is electrically connected with a test port 1 of the test apparatus 30 through the signal switching device 20. D0N is electrically connected with a test port 2 of the test apparatus 30 through the signal switching device 20. Similarly, LEDA is electrically connected with a test port 11 of the test apparatus 30 through the signal switching device 20. As shown in Table 2, VCC is electrically connected with a test port 1 of the test apparatus 30 through the signal switching device 20. LEDK is electrically connected with a test port 2 of the test apparatus 30 through the signal switching device 20. Similarly, IOVCC is electrically connected with a test port 11 of the test apparatus 30 through the signal switching device 20.
FIG. 2 and FIG. 3 schematically show arrangement modes of electrical connectors of the signal switching device 20 when the definition of the ports are shown in Table 1 and Table 2 respectively. As shown in FIG. 2 and FIG. 3, the signal switching device 20 is a matrix-type switching device. The printed wires (tested printed wires) which are connected with each of the tested ports serve as rows of the matrix, and the printed wires (test printed wires) which are connected with each of the test ports serve as columns of the matrix. An intersection point (solid dot as shown in FIG. 2 and FIG. 3) of a row and a column represents an electrical connector for connection between a tested printed wire and a corresponding test printed wire. The arrangement position of the electrical connector is determined by a port definition table that is preset by a manufacturer.
The technical defect of the traditional signal switching device 20 lies in that: when there is no ground wire between adjacent tested printed wires/test printed wires which are used for transmitting a differential signal, signal interference would be generated between the printed wires due to a near distance therebetween. With the increasing of transmission speed and the decreasing of signal amplitude of the LCM, the traditional signal switching device 20 has become a bottleneck in high-speed signal test.